diff --git a/packages/workflow-agent-react/__tests__/tools.test.ts b/packages/workflow-agent-react/__tests__/tools.test.ts
new file mode 100644
index 0000000..6be6661
--- /dev/null
+++ b/packages/workflow-agent-react/__tests__/tools.test.ts
@@ -0,0 +1,101 @@
+import { describe, test, expect, afterAll } from "bun:test";
+import { readFileTool, writeFileTool, patchFileTool, shellExecTool } from "../src/tools/index.js";
+import { join } from "node:path";
+import { tmpdir } from "node:os";
+import { readFileSync, unlinkSync, mkdirSync } from "node:fs";
+import { randomBytes } from "node:crypto";
+
+const TMP_DIR = join(tmpdir(), `tools-test-${randomBytes(4).toString("hex")}`);
+mkdirSync(TMP_DIR, { recursive: true });
+
+const tmpFile = (name: string) => join(TMP_DIR, name);
+
+const cleanupFiles: string[] = [];
+
+afterAll(() => {
+  for (const f of cleanupFiles) {
+    try { unlinkSync(f); } catch { /* ignore */ }
+  }
+  try { unlinkSync(TMP_DIR); } catch { /* ignore */ }
+});
+
+describe("read_file", () => {
+  test("reads file with line numbers", async () => {
+    const p = tmpFile("read-test.txt");
+    cleanupFiles.push(p);
+    const content = "line1\nline2\nline3\n";
+    require("node:fs").writeFileSync(p, content);
+
+    const result = await readFileTool.handler(JSON.stringify({ path: p, offset: null, limit: null }));
+    expect(result).toContain("1|line1");
+    expect(result).toContain("2|line2");
+    expect(result).toContain("3|line3");
+  });
+
+  test("reads with offset and limit", async () => {
+    const p = tmpFile("read-test2.txt");
+    cleanupFiles.push(p);
+    require("node:fs").writeFileSync(p, "a\nb\nc\nd\ne\n");
+
+    const result = await readFileTool.handler(JSON.stringify({ path: p, offset: 2, limit: 2 }));
+    expect(result).toBe("2|b\n3|c");
+  });
+
+  test("returns error for missing file", async () => {
+    const result = await readFileTool.handler(JSON.stringify({ path: "/nonexistent/file.txt", offset: null, limit: null }));
+    expect(result).toContain("Error:");
+  });
+});
+
+describe("write_file", () => {
+  test("writes file and creates dirs", async () => {
+    const p = tmpFile("sub/write-test.txt");
+    cleanupFiles.push(p);
+
+    const result = await writeFileTool.handler(JSON.stringify({ path: p, content: "hello world" }));
+    expect(result).toContain("11 bytes");
+    expect(readFileSync(p, "utf-8")).toBe("hello world");
+  });
+});
+
+describe("patch_file", () => {
+  test("patches file content", async () => {
+    const p = tmpFile("patch-test.txt");
+    cleanupFiles.push(p);
+    require("node:fs").writeFileSync(p, "foo bar baz");
+
+    const result = await patchFileTool.handler(JSON.stringify({ path: p, old_string: "bar", new_string: "qux" }));
+    expect(result).toContain("Successfully");
+    expect(readFileSync(p, "utf-8")).toBe("foo qux baz");
+  });
+
+  test("errors on not found", async () => {
+    const p = tmpFile("patch-test2.txt");
+    cleanupFiles.push(p);
+    require("node:fs").writeFileSync(p, "foo");
+
+    const result = await patchFileTool.handler(JSON.stringify({ path: p, old_string: "xyz", new_string: "abc" }));
+    expect(result).toContain("not found");
+  });
+
+  test("errors on non-unique match", async () => {
+    const p = tmpFile("patch-test3.txt");
+    cleanupFiles.push(p);
+    require("node:fs").writeFileSync(p, "aaa bbb aaa");
+
+    const result = await patchFileTool.handler(JSON.stringify({ path: p, old_string: "aaa", new_string: "ccc" }));
+    expect(result).toContain("not unique");
+  });
+});
+
+describe("shell_exec", () => {
+  test("runs echo", async () => {
+    const result = await shellExecTool.handler(JSON.stringify({ command: "echo hello", timeout: null }));
+    expect(result.trim()).toBe("hello");
+  });
+
+  test("handles timeout", async () => {
+    const result = await shellExecTool.handler(JSON.stringify({ command: "sleep 10", timeout: 1 }));
+    expect(result).toContain("timed out");
+  });
+});
diff --git a/packages/workflow-agent-react/src/index.ts b/packages/workflow-agent-react/src/index.ts
index 5f1961f..c5ce881 100644
--- a/packages/workflow-agent-react/src/index.ts
+++ b/packages/workflow-agent-react/src/index.ts
@@ -1,2 +1,4 @@
 export { createReactAdapter } from "./create-react-adapter.js";
 export type { ReactAdapterConfig, ReactToolHandler } from "./types.js";
+export { defaultTools, defaultToolHandler } from "./tools/index.js";
+export type { ToolEntry, ToolHandler } from "./tools/index.js";
diff --git a/packages/workflow-agent-react/src/tools/defaults.ts b/packages/workflow-agent-react/src/tools/defaults.ts
new file mode 100644
index 0000000..906d610
--- /dev/null
+++ b/packages/workflow-agent-react/src/tools/defaults.ts
@@ -0,0 +1,16 @@
+import type { ToolDefinition } from "@uncaged/workflow-reactor";
+import type { ToolEntry } from "./types.js";
+import { readFileTool } from "./read-file.js";
+import { writeFileTool } from "./write-file.js";
+import { patchFileTool } from "./patch-file.js";
+import { shellExecTool } from "./shell-exec.js";
+
+const ALL_TOOLS: ToolEntry[] = [readFileTool, writeFileTool, patchFileTool, shellExecTool];
+
+export const defaultTools: readonly ToolDefinition[] = ALL_TOOLS.map((t) => t.definition);
+
+export async function defaultToolHandler(name: string, args: string): Promise<string> {
+  const entry = ALL_TOOLS.find((t) => t.definition.function.name === name);
+  if (!entry) return `Unknown tool: ${name}`;
+  return entry.handler(args);
+}
diff --git a/packages/workflow-agent-react/src/tools/index.ts b/packages/workflow-agent-react/src/tools/index.ts
new file mode 100644
index 0000000..6c4dfe0
--- /dev/null
+++ b/packages/workflow-agent-react/src/tools/index.ts
@@ -0,0 +1,6 @@
+export { readFileTool } from "./read-file.js";
+export { writeFileTool } from "./write-file.js";
+export { patchFileTool } from "./patch-file.js";
+export { shellExecTool } from "./shell-exec.js";
+export { defaultTools, defaultToolHandler } from "./defaults.js";
+export type { ToolEntry, ToolHandler } from "./types.js";
diff --git a/packages/workflow-agent-react/src/tools/patch-file.ts b/packages/workflow-agent-react/src/tools/patch-file.ts
new file mode 100644
index 0000000..6402a34
--- /dev/null
+++ b/packages/workflow-agent-react/src/tools/patch-file.ts
@@ -0,0 +1,40 @@
+import { readFile, writeFile } from "node:fs/promises";
+import type { ToolEntry } from "./types.js";
+
+export const patchFileTool: ToolEntry = {
+  definition: {
+    type: "function",
+    function: {
+      name: "patch_file",
+      description: "Find and replace a string in a file (first occurrence only).",
+      parameters: {
+        type: "object",
+        properties: {
+          path: { type: "string", description: "Path to the file" },
+          old_string: { type: "string", description: "Text to find" },
+          new_string: { type: "string", description: "Replacement text" },
+        },
+        required: ["path", "old_string", "new_string"],
+      },
+    },
+  },
+  handler: async (args: string): Promise<string> => {
+    try {
+      const parsed = JSON.parse(args) as { path: string; old_string: string; new_string: string };
+      const content = await readFile(parsed.path, "utf-8");
+      const firstIdx = content.indexOf(parsed.old_string);
+      if (firstIdx === -1) {
+        return `Error: old_string not found in ${parsed.path}`;
+      }
+      const secondIdx = content.indexOf(parsed.old_string, firstIdx + 1);
+      if (secondIdx !== -1) {
+        return `Error: old_string is not unique in ${parsed.path} (found multiple occurrences)`;
+      }
+      const updated = content.slice(0, firstIdx) + parsed.new_string + content.slice(firstIdx + parsed.old_string.length);
+      await writeFile(parsed.path, updated);
+      return `Successfully patched ${parsed.path}`;
+    } catch (err) {
+      return `Error: ${err instanceof Error ? err.message : String(err)}`;
+    }
+  },
+};
diff --git a/packages/workflow-agent-react/src/tools/read-file.ts b/packages/workflow-agent-react/src/tools/read-file.ts
new file mode 100644
index 0000000..577dbac
--- /dev/null
+++ b/packages/workflow-agent-react/src/tools/read-file.ts
@@ -0,0 +1,35 @@
+import { readFile } from "node:fs/promises";
+import type { ToolEntry } from "./types.js";
+
+export const readFileTool: ToolEntry = {
+  definition: {
+    type: "function",
+    function: {
+      name: "read_file",
+      description: "Read a text file and return lines with line numbers.",
+      parameters: {
+        type: "object",
+        properties: {
+          path: { type: "string", description: "Path to the file to read" },
+          offset: { type: ["number", "null"], description: "Start line number (1-indexed, default: 1)" },
+          limit: { type: ["number", "null"], description: "Max lines to read (default: all)" },
+        },
+        required: ["path"],
+      },
+    },
+  },
+  handler: async (args: string): Promise<string> => {
+    try {
+      const parsed = JSON.parse(args) as { path: string; offset: number | null; limit: number | null };
+      const content = await readFile(parsed.path, "utf-8");
+      const allLines = content.split("\n");
+      const offset = parsed.offset ?? 1;
+      const start = Math.max(0, offset - 1);
+      const end = parsed.limit != null ? Math.min(allLines.length, start + parsed.limit) : allLines.length;
+      const lines = allLines.slice(start, end);
+      return lines.map((line, i) => `${start + i + 1}|${line}`).join("\n");
+    } catch (err) {
+      return `Error: ${err instanceof Error ? err.message : String(err)}`;
+    }
+  },
+};
diff --git a/packages/workflow-agent-react/src/tools/shell-exec.ts b/packages/workflow-agent-react/src/tools/shell-exec.ts
new file mode 100644
index 0000000..fa54461
--- /dev/null
+++ b/packages/workflow-agent-react/src/tools/shell-exec.ts
@@ -0,0 +1,45 @@
+import { execSync } from "node:child_process";
+import type { ToolEntry } from "./types.js";
+
+const MAX_OUTPUT = 10000;
+
+export const shellExecTool: ToolEntry = {
+  definition: {
+    type: "function",
+    function: {
+      name: "shell_exec",
+      description: "Execute a shell command and return stdout + stderr.",
+      parameters: {
+        type: "object",
+        properties: {
+          command: { type: "string", description: "Shell command to run" },
+          timeout: { type: ["number", "null"], description: "Timeout in seconds (default: 30)" },
+        },
+        required: ["command"],
+      },
+    },
+  },
+  handler: async (args: string): Promise<string> => {
+    try {
+      const parsed = JSON.parse(args) as { command: string; timeout: number | null };
+      const timeoutMs = (parsed.timeout ?? 30) * 1000;
+      const output = execSync(parsed.command, {
+        encoding: "utf-8",
+        timeout: timeoutMs,
+        stdio: ["pipe", "pipe", "pipe"],
+        maxBuffer: MAX_OUTPUT * 2,
+      });
+      return output.length > MAX_OUTPUT ? `${output.slice(0, MAX_OUTPUT)}\n...(truncated)` : output;
+    } catch (err: unknown) {
+      if (err && typeof err === "object" && "status" in err && (err as { status: unknown }).status === null) {
+        return "Error: command timed out";
+      }
+      if (err && typeof err === "object" && "stderr" in err) {
+        const e = err as { stderr: string; stdout: string; status: number };
+        const combined = `${e.stdout ?? ""}${e.stderr ?? ""}`;
+        return combined.length > MAX_OUTPUT ? `${combined.slice(0, MAX_OUTPUT)}\n...(truncated)` : combined || `Error: command exited with status ${e.status}`;
+      }
+      return `Error: ${err instanceof Error ? err.message : String(err)}`;
+    }
+  },
+};
diff --git a/packages/workflow-agent-react/src/tools/types.ts b/packages/workflow-agent-react/src/tools/types.ts
new file mode 100644
index 0000000..255094a
--- /dev/null
+++ b/packages/workflow-agent-react/src/tools/types.ts
@@ -0,0 +1,8 @@
+import type { ToolDefinition } from "@uncaged/workflow-reactor";
+
+export type ToolHandler = (args: string) => Promise<string>;
+
+export type ToolEntry = {
+  definition: ToolDefinition;
+  handler: ToolHandler;
+};
diff --git a/packages/workflow-agent-react/src/tools/write-file.ts b/packages/workflow-agent-react/src/tools/write-file.ts
new file mode 100644
index 0000000..f6a2e74
--- /dev/null
+++ b/packages/workflow-agent-react/src/tools/write-file.ts
@@ -0,0 +1,32 @@
+import { mkdir, writeFile } from "node:fs/promises";
+import { dirname } from "node:path";
+import type { ToolEntry } from "./types.js";
+
+export const writeFileTool: ToolEntry = {
+  definition: {
+    type: "function",
+    function: {
+      name: "write_file",
+      description: "Write content to a file, creating parent directories as needed.",
+      parameters: {
+        type: "object",
+        properties: {
+          path: { type: "string", description: "Path to write" },
+          content: { type: "string", description: "File content" },
+        },
+        required: ["path", "content"],
+      },
+    },
+  },
+  handler: async (args: string): Promise<string> => {
+    try {
+      const parsed = JSON.parse(args) as { path: string; content: string };
+      await mkdir(dirname(parsed.path), { recursive: true });
+      const buf = Buffer.from(parsed.content, "utf-8");
+      await writeFile(parsed.path, buf);
+      return `Successfully wrote ${buf.length} bytes to ${parsed.path}`;
+    } catch (err) {
+      return `Error: ${err instanceof Error ? err.message : String(err)}`;
+    }
+  },
+};